A Thorough QT Study to Evaluate the Effects of Supratherapeutic Doses of Ledipasvir on the QTc Interval in Healthy Subjects

Sofosbuvir: Really Meets the Unmet Needs for Hepatitis C Treatment?

Chronic hepatitis C remains a major public health concern with a prevalence of more than 1% worldwide. Of late, with the discovery of newer drugs, chronic HCV treatment has touched new dimensions. The treatment has progressed from Interferons to Pegylated interferon (Peg IFN) based therapy, with or without ribavirin to treatment with orally active Direct Acting Antivirals (DAA) with Peg IFN and ribavirin and eventually to various combinations of DAA, without IFN. Introduction of newer DAAs has transfigured the treatment of chronic HCV. Chronic HCV patients with advanced liver disease, psychiatric condition, anemia or autoimmune diseases, not eligible for Peg IFN based therapy have a ray of hope now. Amongst all DAAs, nucleoside inhibitors have been the most promising agent. Thus the present review focuses on Sofosbuvir, one of the most effective nucleoside inhibitors; in terms of potency, resistance profile, activity against all genotypes of HCV and adverse effects. FDA approved Sofobuvir for clinical use in 2013. Chemically, it is 2'-deoxy-2'-α-fluoro-β-Cmethyluridine- 5'-triphosphate; a phosphoramidate prodrug that is activated by enzyme present in human liver. It is a highly potent inhibitor of HCV NS5B polymerase. Efficacy of the Sofosbuvir has been established in various phase 2 and phase 3 clinical trials like PROTON, ELECTRON, FUSION, POSITRON etc. Sofosbuvir has a good safety profile with few mild to moderate adverse effects. Evidence reveals that sofosbuvir has substantial impact on the treatment of HCV.

Direct-acting antiviral interactions with opioids, alcohol or illicit drugs of abuse in HCV-infected patients

The hepatitis C virus (HCV) prevalence is extremely high in patients who consume and inject illicit drugs. Concerns about poor adherence and fear of interaction with drugs of abuse could constitute further disincentive for treatment initiation in these patients. We discussed the pharmacokinetics (PKs) and pharmacodynamics (PD) of currently prescribed direct antiviral agents (NSA5 inhibitors: daclatasvir, elbasvir, ledipasvir, pibrentasvir, velpatasvir; NS5B inhibitor: sofosbuvir; NS3/4A protease inhibitors: glecaprevir, grazoprevir, voxilaprevir) and most common substances of abuse (opioids: buprenorphine, fentanyl, heroin, methadone, morphine, oxycodone; stimulants: amphetamines, cathinones, cocaine; cannabinoids; ethanol). Overall, most direct-acting antivirals (DAAs) are substrates and inhibitors of the transmembrane transporter P-glycoprotein (P-gp), and several of them are metabolized by cytochrome P450 enzymes. Clinically relevant interactions are associated with P-gp and CYP3A modulators. Most substances of abuse are eliminated by Phase I and Phase II metabolizing enzymes, but none of them are either major inhibitors or inducers. PK studies did not show any relevant interactions between DAA and methadone or buprenorphine. Based on pharmacological considerations, neither efficacy loss nor adverse drug event associated with detrimental interaction are expected with opioids, stimulants, cannabinoids and ethanol. In summary, our literature review shows that the interaction potential of DAA with most opioids and illicit drugs is limited and should not be a hurdle to the initiate DAA.

Drug-Drug Interaction Profile of the Fixed-Dose Combination Tablet Regimen Ledipasvir/Sofosbuvir

Ledipasvir/sofosbuvir (Harvoni^®), a fixed-dose combination tablet of an NS5A inhibitor ledipasvir and an NS5B polymerase inhibitor sofosbuvir, is approved for the treatment of chronic hepatitis C virus infection. Ledipasvir/sofosbuvir exhibits a favorable drug-drug interaction profile and can be administered with various medications that may be used by hepatitis C virus-infected patients, including patients with comorbidities, such as co-infection with human immunodeficiency virus or immunosuppression following liver transplantation. Ledipasvir/sofosbuvir is not expected to act as a victim or perpetrator of cytochrome P450- or UDP-glucuronosyltransferase 1A1-mediated drug-drug interactions. With the exception of strong inducers of P-glycoprotein, such as rifampin, ledipasvir/sofosbuvir is not expected to act as a victim of clinically relevant drug-drug interactions. As a perpetrator of pharmacokinetic drug-drug interactions via P-glycoprotein/BCRP, ledipasvir/sofosbuvir should not be used with rosuvastatin and elvitegravir/cobicistat/emtricitabine/tenofovir disoproxil fumarate, whereas its co-administration with amiodarone is not recommended because of a pharmacodynamic interaction. This review summarizes a number of drug interaction studies conducted in support of the clinical development of ledipasvir/sofosbuvir.